1. Field of the Invention
The invention relates to Color measuring apparatus and more particularly to colorimeters.
2. Background Art
Color measuring instruments for various applications are well known and described in various text books. A variety of different types of color measurements may be taken for different purposes. The measurement of color has had commercial application for many years. It is used, for example, to determine color consistency in photograph as well as the characteristics of color of printed materials, textiles, automobiles, etc. Different instruments are used for different purposes. The most comprehensive color measurements are obtained by instruments known as spectrophotometers which measure spectral distribution of light and give a percentage reflection or transmission at many points in the visible spectrum. These instruments are generally used for color appearance measurements. However, not all applications require the sophistication and accuracy of the spectrophotometer. Densitometers measure color density and are typically used for measuring specific materials such as printing inks and photographic dyes. Where specific color information is desired without the need for the sophistication of a spectrophotometer, a colorimeter may be used. The colorimeter is a tri-stimulant instrument which measures reflectance or transmittance through color filters which are properly related to properties of the human eye. The colorimeter is useful in photographic and color printing and reproduction applications as well as other applications.
The field of desk top publishing has expanded greatly in recent years and color printers have become ubiquitous. Color printers are often controlled by a program controlled processor which transmits control signals to the printer defining color to be produced. To assure color quality, it is desirable to be able to calibrate color printers to produce a selected quality of color for printed material produced by a number of different printers. Additionally, with increased data communication, data defining a color product may be transmitted to remote locations to be printed by a variety of printers. In order to be able to provide a product of consistent color characteristics, a comparison to a color standard is required. It is, therefore, desirable to provide a portable and inexpensive colorimeter which can be used to compare color characteristics of printed materials at various locations. Furthermore, it is desirable to provide an automatic scanning apparatus which can automatically scan color bars typically printed along an edge of color printed sheets.